How to Understand the Difference Between TTL Versus Manual Flash Modes

It is no secret that the popup flash which comes built-in to your digital camera simply isn’t enough in most situations. For a variety of reasons, shooting using just the popup flash is not a feasible option. That is why you will find photographers everywhere you look, going for an external flash and using it increasingly during their shoots.

External flash, also known by the term “speedlight” provides many benefits and advantages to photographers, even while shooting in extremely low light conditions. They allow us to have a far superior control over the lighting of an image. Flashes are available in the market from a variety of manufacturers including camera makers like Canon and Nikon, or third-party companies like Godox, Yongnuo, Nissin, etc.

If you step out in the market to buy your first flash, you will come across two variants, a fully manual flash, and a TTL (Through The Lens) flash. You may end up getting confused over which flash will suit you the best and which one you should invest your money in. Both the Manual and TTL flash have their own plus and minus points which appeal to photographers. What is important is to properly understand their systems, functionalities, advantages, and disadvantages.

Understanding Manual Flash

On a fully Manual flash, there is no control (d either by the camera or the flash) over the intensity or duration of the light emitted from the flash. Instead, it is the photographer who controls the output of the flash by adjusting the settings, either in-camera or on the flash itself.

While using a manual flash, there are four controls you can use to set your flash output manually as per your requirements:

Manual mode – check the user manual for your flash to see how to set it.

Not all flashes are equal

An important point to remember and consider is that the majority of flashes can shoot in manual mode, but not every flash can shoot in TTL mode. A manual flash also gives you specific control over the light and exposure, and allows you to set it exactly to your requirements. You do not have to use exposure compensation while using a manual flash as your composition, frame, etc., does not have any affect on the overall exposure and lighting of the scene.

Pros and cons of manual flash

In situations where the distance between the flash and the subject is constant and fixed, you can opt to use manual flash settings. A manual flash is extremely useful in situations where you have to fire away a series of shots of the subject repeatedly, under similar exposure conditions. E.g., in food photography, product shoots, and more this is the case. The power level is fixed, and it remains the same, which ensures that the exposure does not vary from shot to shot.

Manual flash works best when the subject is not moving like this setup, posed shot.

One of the main drawbacks of using a flash in manual mode is that you still need to figure out the optimal power output needed to obtain the correct exposure, which can be a time consuming process. And thus, a manual flash can mainly be used while shooting portraits, headshots, and fine art. In other words, in situations where you can take time to setup the scene.

Many also believe that manual mode is the best to use to learn about external flash photography. You choose the output, click the picture and then review it. If it does not come out the way you were expecting and wanted it to, then you can tweak the settings and try again. So you end up learning more in the process.

Understanding Automatic or TTL Flash

When the flash output is directly controlled by your camera, it is called Through-the-Lens metering or TTL. In the case of an Automatic or TTL enabled flash, the flash output is directly controlled by the flash or by the camera’s exposure metering system. Thus, using a flash in TTL mode will give you varied flash output.

Flash in TTL or Automatic mode.

The only method to control a TTL enabled flash is to use the flash exposure compensation function on the flash or through your camera settings. Also, while using a TTL flash, your chosen Aperture and ISO levels do not affect the flash output because the camera tells the flash to emit a particular output based on the camera’s readings. If the settings change, so will the output to compensate automatically.

When you half-press our shutter release button on your camera to focus, your camera not only focuses, but it also takes a metering of the scene and its exposure. It measures the amount of ambient light which is being returned “Through the Lens” to the sensor.

How it works

A TTL enabled flash fires a “pre-flash” before the actual shot is taken. The camera then measures the pre-flash with the ambient light level to calculate the power needed from the actual flash to make a correct exposure. This pre flash happens really quickly, only micro-seconds before the main flash, and thus cannot be seen by the human eye. Based on the model of your flash, this pre-flash can be an actual white light flash or an infrared one.

Using a TTL enabled flash is extremely helpful in situations when you are moving around a lot, shooting in different or changing lighting settings, etc., and do not have the time to fire a series of test shots before the shoot.

One of the drawbacks which accompany the use of a TTL flash is less control and less precision over the lighting. If you get an incorrect exposure while using a flash in TTL mode, it is really difficult for you to know the power setting which was used for that shot.

Conclusion

If you have recently purchased your first digital camera and plan to buy an external flash, then you have two options.

Either go for a manual flash, as it will urge you to learn more about how to control and adjust the lighting in various situations. But if you want to take up professional assignments and cannot afford to experiment with a manual flash, then go for a TTL enabled flash.

Which do you use? Do you have a flash that does both? Which do you prefer for different situations? Please tell us in the comments below.

Kunal Malhotra
is a photography enthusiast whose passion for photography started 6 years back during his college days. Kunal is also a photography blogger, based out of Delhi, India. He loves sharing his knowledge about photography with fellow aspiring photographers by writing regular posts on his blog. Some of his favorite genres of photography are product, street, fitness, and architecture.